For example, a step-down type of DC-DC converter is used in information equipment. Such a DC-DC converter employs a switching power supply using a switch. FIG. 2 of Patent Document 1 and FIG. 29 of Patent Document 2 disclose a switching power supply configured so that a series circuit of a transient current switch and a capacitor is connected in parallel with a switch, and a resistor is connected in parallel with the capacitor.
According to Patent Documents 1 and 2, a transient current that flows when the switch is turned on/off is stored in the capacitor, and the charge stored in the capacitor is consumed by the resistor.    [Patent Document 1] Japanese Laid-Open Patent Publication No. 2006-173717    [Patent Document 2] International Publication Pamphlet No. 2005/041231